The invention concerns a heat sink of metallic material, in particular a light metal alloy, for semi-conductor elements or similar components, with cooling ribs projecting from a base plate parallel to each other and spaced apart, with approximately rod-like cross section, and which protrude into the base plate with a connection strip. The invention also comprises a process for the production of these and a molding tool for these.
DE 35 18 310 C2 discloses a heat sink with a base plate of an AlMgSi alloy extruded in an extrusion die as a molding tool, in the surface of which body are formed insert grooves for the plate-like cooling ribs made from a sheet or profile. The ribs have a base which, after insertion in one of the grooves, is distorted by a caulking process. With very close rib spacing and deep cooling ribs, the load on the caulking chisel is so great that it quickly kinks. In other known cooling bodies the cooling ribs can be glued or soldered in place. Gluing has the disadvantage that the glue causes a deterioration in the heat transmission from the base plate or plinth to the cooling rib. For soldering, again costly preliminary treatment is required.
For another heat sink according to DE 25 02 472 C2, the base plate is also produced with grooves, the walls of which in their longitudinal direction are fitted with pressed-out wall ribs. Cooling ribs with vertical fluting are pressed in these grooves by means of cold pressure welding. The necessary high forces which must be applied in the cold pressure welding process greatly limit the length of the cooling bodies to be produced, and a minimum thickness of cooling ribs is required in order to avoid their kinking during the cold pressure welding process.
It is not only the forces occurring which limit the length of the cooling body. The vertical fluting of the cooling ribs limits their length measured along the base plate due to the dimensions of the extrusion tool as the pressing direction is the same as the fluting direction.
Accordingly, it is an object of the present invention to provide a cooling body which does not have the defects described. Also, the heat conductivity or control of heat conduction is improved.
The foregoing object is achieved wherein, the base plate consisting of metal material is cast onto the metallic cooling ribs in the area of their connection strips, i.e. no subsequent insertion and deformation processes are required. The casting process also allows integration of inserts of heat conductive material to increase the conductivity and to control the heat conduction.
According to a further feature of the invention, at least one insert of good conductive material is cast into the base plate; as inserts, preferably heat pipes to control the heat conduction can be used.
Favourably, several heat pipes are used as inserts which run parallel to each other and to the faces of the base plate. Also, the inserts extend between the parallel sides of the base plate.
The scope of the invention includes a process for production of such a cooling body in which, to form cooling ribs, plate-like moldings are arranged at intervals in a mold, approximately parallel to each other so that their connection strips of specific height protrude into the chill mold chamber for the base plate, and this mold chamber is filled with the metallic material as a casting compound; when this hardens, the connection strips are held firmly by the base plate and subsequently form a unit with this.
To simplify the casting process, by the use of intermediate layers parallel to each other receiver gaps for the plate-like moldings are produced and the latter inserted in the receiver gaps, whereupon two side walls parallel to the intermediate layers are brought together under pressure in order to create a compact mold for preparation of the casting.
According to a further feature of the invention, before filling with the hot casting compound, inserts of heat conductive material are arranged in the mold chamber in order to be cast into the base plate.
As a molding tool according to the invention, a casting mold is used with a mold chamber for the base plate or plinth, to which, before the actual casting process, are allocated the parallel cooling ribs made from a sheet or profile so that their foot edges and adjacent connection strips protrude into the area established for the casting compound and are there held by the latter during the casting process; after hardening of the casting compound, the cooling body with metal constituents connected internally is then ready for use.
In the molding tool according to the invention, two parallel side walls, and intermediate layers between them and also parallel, are arranged displaceably on at least one shaft passing through them; the plate-like moldings are pressed into the receiver gaps bordered by the intermediate layers until they contact the shaft(s), the side walls are then compressed in the shaft direction until a compact casting mold is achieved. Its mold base is substantially determined by the foot edges of the intermediate layers.